Coating and treating material



Jan. 9, 1945. R. LLMELTON 2,366,926

COATING AND TREATING MATERIAL Filed Jan. 5, 1942 5 Sheets-Sheet l 72 Ira-Junior Ron/E N51. TO

Jan. 9, 1945 R. MELTON 2,366,926

COATING AND TREATING MATERIAL Filed Jan. 5, 1942 3 Sheets-Sheet 2 ATTORNEY Jan. 9, 1945. R. L. MELTON COATING AND TREATING MATERIAL Filed Jan. 5, 1942 3 Sheets-Sheet 3 [nven't'on llM/E L. M51. TON

Patented Jan. 9, 1945 COATING AND TREATING MATERIAL Romie L. Melton, Niagara Falls, N. Y., assignor to The Carborundum Company, Niagara Falls, N. Y, a corporation of Delaware Application January 5, 1942, Serial No. 425,621

2 Claims.

This invention relates to the manufacture of coated webs of such material as paper, cloth, and the like, particularly those having a granular coating thereon.

The object of the invention is to provide improved apparatus for applying adhesive coatings to webs and for subsequently treating them by the use of a high-velocity gas jet impinging on the coated surface. This and other objects will become apparent in the following disclosure.

The present invention provides, in one embodiment thereof, an apparatus by which an abrasive coated web, formed by coating a moving web' with a coating of adhesive and applying a layer of abrasive grains to the adhesively coated sheet,

has applied thereto a sizing layer of adhesive over the layer of abrasive grains, as by use of a roll applicator, and subjecting the thus coated web to the action of a jet of gas, extending across the full width of the web, said gas containing adhesive in atomized or finely divided form. The gas jet clears the size coating from abrasive granule tips and drives the size coating down into the valleys between grains, and the adhesive carried by the gas reinforces said sizing coat between grains. The adhesive carried by the gas jet may be altogether different from the sizing coat. If desired, it may be a waterproof adhesive or it may be a waterproofing solution for the sizing coat.

The invention will be better understood by reference to the accompanying drawings, in which:

Figure 1 is an enlarged cross-section of the web taken on the line I-I in Figure 4;

Figure 2 is a similar view taken on the line 22 in Figure 4;

Figure 3 is a similar view taken onthe line 33 in Figure 4;

Figure 4 is a schematic view of apparatus for size coating abrasive coated webs, with means for clearing the abrasive granule tips and for applying an additional layer of adhesive;

Figure 5 is a detailed side elevation of the adhesive applying mechanism shown diagrammatically in Figure 4;

Figure 6 is a front view of the apparatus shown in Figure 5; and

Figure 7 is a detailed cross section of the air jet and spray device taken on the line 'I--'I in Figure 6.

Figure 1 illustrates a fragment of an abrasive coated web material 2 prior to application of the sizing or reinforcing layer of adhesive. The

backing 2 may be of any of the usual flexible materials such as paper, cloth, vulcanized fiber,

or a combination of these or other suitable materials. Adhesive 3 may be a glue, varnish, silicate, or synthetic resin. The particles of abrasive grain 4 are shown in oriented or upstanding position with respect to the backing, and are so deposited onto the adhesive base coating 3 by suitable means not shown in the present application. As shown in Figure 1, only the bottoms of the granules 4 are in contact with the base layer of adhesive 3. This gives a very limited and insufficient support to the abrasive granules to maintain them against lateral pressure and grinding stresses when the coated web is used as an abradant. 'It is necessary, therefore, to apply additional adhesive around the bases of the abrasive granules I so as to anchor them more firmly to the base coating and web backing material 2. t

Figure 2 shows a granular coated web produced by the usual process, in which a blanket of adhesive 5 was applied over the granular coated surface and permitted to flow down between the grains of its own accord. The tips of the granular particles I are covered with a film of adhesive indicated by the reference 9. This film of adhesive is very detrimental when the coated material is used for abrasive purposes, since the tips of the grains are capped with the adhesive. Furthermore, voids 8a, 8b, 8c, 8d are apt to be formed under any overhanging parts of the granules, thus producing a weak bond.

Figure 3 illustrates a fragment of an abrasive coated web made in accordance with one modification of the invention. This product has the sizing coat 5 driven down into the valleys between granules, the tips of the granules: cleared of adhesive, and an additional coating 6a of a suitable material, which may be additional adhesive of such character as to strengthen or waterproof the sizing coat 5.

The procedure in manufacturing granular coated webs of the character shown in Figure 3 will now be described.

The previously coated abrasive material, such as that illustrated by Figure 1, is moved from suitable drying racks (not shown) by means of the suction drum I I, Figure 4, passed around the rubber covered idler rolls I2, I3, and I4, and between the adhesive roll I5 and cooperating pressure roll I6. The rubber-covered adhesive roll I5 is partially immersed and revolves in the liquid adhesive contained in the pan II so that a layer of sizing adhesive is applied to the abrasive side of the coated web. The pressure roll I6 is adjustably supported above the adhesive roll and provided with adjusting means (see Figure whereby the spacing between the rolls may be varied and thereby regulate the quantity or thickness of the layer of adhesive applied to the abrasive side of the coated web.

After passing between the adhesive applying rolls l5 and IS, the coated web is moved past a jet of high velocity gas with entrained adhesive in atomized or finely divided form issuing from the adjustable orifice 3! at the rear of the gas jet or air knife generally indicated by the reference numeral 30 The device 30 is provided at one side with a gas inlet 44 and a nozzle means 45 for projecting finely divided liquid adhesive into the incoming stream of gas from inlet 44. The resulting jet of high velocity gas with entrained finely divided droplets of adhesive from orifice 3i serves to drive the freshly applied layer of adhesive 5 from the tips of the abrasive grains and to cause it to fiow down and around the bases of the grains. At the same time the entrained adhesive or other substance is deposited on the sizing coat to form an additional layer indicated at 6a. Because of the velocity with which this adhesive is projected, it does not adhere to the granule tips. Furthermore, because of the flowing of the sizing coat 5 under the action of the air jet, the line of demarcation 6 between coats 6a and 5 is not sharp, since the additional adhesive is driven into and mixed with the sizing coat for a considerable depth at the interface between layers 6a and 5. For that reason, adherence between layers 5 and 5a is very 'good and, since it is keyed into layer 5 in such manner, it seals the top of the sizing coat on the abrasive product effectively from the atmosphere.

The coated web then passes over the suction drum 40 and idler roll 4| to asuitable drying rack, where it is formed in loops by the festooning device 42 and hung on the supporting bars 43 in a drying or curing chamber to set the adhesive fully. After drying or curing, the coated web is taken down from the rack and cut into pieces of various sizes.

In the air jet device schematically shown in Figure 4, the material introduced into the "air knife may, as an alternative to a liquid, be an adhesive in the form of a finely divided powder, and may be forced through the nozzle means 45. The pressure on the finely divided material at the nozzle or opening, plus the temperature of the incoming gas stream and the action of a solvent carried by the gas stream melt the powder to a liquid form.

The air knife" and its incorporated material spraying means shown schematically in Figure 4, and the specific embodiment shown in Figures 5, 6, and '7 and subsequently to be described, may be used to carry out various processes other than that above described in applying and conditioning adhesive coatings on various materials.

As one example, the web backing material for a flexible abrasive may be coated in a conventional manner with a heavy viscous adhesive layer such as heavy glue, silicate, resin, etc. The coated material is then passed, while suitably supported, under an air knife having an incorporated spray means. The additional adhesive may be of glue, of less viscosity than the first layer of adhesive. The air jet from the air knife smooths and levels the first layer of adhesive and drives against it the second adhesive, which is likewise leveled on top of the first, and modifies and conditions the first layer for optimum reception and retention of abrasive granules to be applied.

As another example, a base or making layer of adhesive is applied in a conventional manner to a web backing, a layer of abrasive granules is deposited thereon, and such coated web is then passed, while suitably supported, under an air knife" having an incorporated spraying means. In this instance the spraying means is supplied with an adhesive suitable for use as a sizing coat on the abrasive coated sheet and which softens the top of the first applied adhesive layer as it contacts it in the valleys between abrasive granules. Because of the velocitywith which the second adhesive is projected, it does not adhere to the abrasive granule tips, but is driven between them, thus insuring a strong lateral support for the granules in the finished product.

Referring now to Figures 5, 6, and '7, the construction and operation of one embodiment of the air knife with incorporated spray means will be described in detail. The adhesive pan I1 is supported We suitable frame 20, which also supports the adhesive oll I5 in such manner that said roll revolves in a liquid adhesive and applies a film or layer of said adhesive to the coated web I. naled on the frame 20 and adapted to be adjusted vertically by means of the handwheel 2| and screw-threaded shaft 22. Such vertical adjustment of the pressure roll l5 varies the spacing between the coated web I and the adhesive roll l5 and thereby regulates the thickness of the layer of adhesive applied to the moving web. With a wide spacing between the rolls, a thick layer of adhesive will be applied, and with a close spacing, a relatively thin film of adhesive will be applied.

The air knife 30 with its incorporated spray means is mounted on the bearing 23 by a suitable bracket 24 and moves up or down with any vertical adjustment of the pressure roll l5. Thus the adjustment of the air knife" with respect to the surface of the coated web remains constant regardless of any vertical adjustment of the roll l6. However, the jet is adjustable with respect to the roll I6 and web I and means are provided for both angular and horizontal movement of the "air knife. Cradle supports 25 are suitably mounted in gibs 26 secured to the bracket 24 and adapted to be moved horizontally by means of the small handwheel 21 and screwthreaded shaft 28 which are journaled on the bracket 24 and engage a threaded portion of the base of the said cradle 25. By loosening the clamping bolt 29, the jet 30 may be tilted by means of the handles 33 to any desired angle so that the impingement of the gas stream against the coated web can be at an angle of thereto or at any desired oblique angle, as indicated by the arrow 35 in Figure 4.

The thickness of the stream of gas with entrained particles of adhesive which issues from orifice 3| may be adjusted by means of bolts 32 and 32a which regulate the orifice opening of the jet 30. from .002" to approximately .025" and may extend the full width of the web I or, if desired, a number of such jets may be employed to cover the entire width of the web. A jet of approxi- 1 mately .005" in thickness is satisfactory for most The pressure roll I6 is also jour- This orifice opening is adjustable crease or decrease this distance, depending upon the type of adhesive sprayed through orifice 3|.

The gaseous medium is supplied to the spray means incorporated in jet 38 by means of a flexible hose connection 46 which connects to a suitable source of supply not shown. Hose 46 connects through regulating valve 41a with a cross pipe 41, which feeds five vertical pipes 48 leading to spaced spray means, shown generally in Figures'fi and 7 as 49, on the front of the jet 30.

Five such inlets are shown, spaced to give substantially uniform distribution of the atomized adhesive over the width of the jet 38. Obviously in certain cases, as when the air knife" width is relatively small, only one spray means needs to be used. Furthermore, more than five spray means may be employed if found necessary to produce the desired uniformity of distribution under certain conditions. Pipe 41 is heat insulated by covering 51. The adhesive medium to be sprayed is supplied to spray means 49 by means of a flexible hose connection 53, which connects to a suitable source of supply not shown.

The adhesive flows from hose 53 into a cross pipe 52, which in turn connects with vertical pipes leading to the spray means 49 on the front portion of jet 30. Adhesive supply pipe 52 is jacketed by concentric tube 54, to which is connected inlet hose 55 and outlet hose 56. A heating medium such as hot water or steam is flowed through jacket 54 for the purpose of keeping the adhesive in pipe 52 at proper temperature and thus of sufliciently low viscosity to be sprayed readily.

The main supply of gaseous medium to the jet 38 is supplied to the jet through an opening 34a (Fig. 7) in the end wall and trunnion therefor by means of a flexible hose connection 34, which connects to a suitable source of supply, not shown. The internal construction of the jet 38 is such that the gas pressure is equalized and the stream of gas issuing from the orifice is of uniform velocity throughout, and so that the emergent gas stream is substantially non-divergent. The velocity of this gas stream appears to be of considerable magnitude, although it is difficult to express in actual units. It has been found, however, that the required velocities may be obtained with a suitably designed jet at relatively low gas pressures ranging from-2 to p. s. i. gage and when an,oriflce opening of ap proximately .005 of -an inch is employed, the gas velocity, and hence the gage pressure, required will, of course, depend upon the character,

- condition and thickness of the particular sizing adhesive being used. With thick viscous ad- 'hesives employed as the sizing coat on Web I in Figure 4, a high gas pressure will be required, and with thin or less viscous adhesives, a relatively lower pressure will be required to clear such adhesive from the tips of the granular particles and produce a supporting mound of adhesive around the bases of the granules.

As shown in Figure 7, each spray means 49 is mounted on a boss 58 on the front of jet by means of bolts 59 threaded into the boss and passing through flange 68 on the spray means. The spray means 49 consists of a main body 6|- having a transverse passage 62 therein connected outwardly to the adhesive supply pipe 5| and inwardly to an axial passage63. Another transverse passage 64 communicates outwardly with the gaseous medium supply pipe 48 and inwardly with passage 65 which is parallel with the longitudinal axis of the spray means and separated from passage 63 by partition 66. The outer end of body BI is provided with a cylindrical coaxial projection 61 on which cover plate 68 is secured by bolts 69. A valve stem l8 projects through an axial hole in plate 68, and has. threaded engagement therewith; said valve stem also extends through the cylindrical axial guide opening 12 in the body BI and has a fluid tight connection therewith by reason of the packing gland indicatedgenerally at 13. The valve stem is provided with an operating hand wheel 50 on its outer end, and with a lock nut 14 having threaded engagement therewith and abutting the outer face of plate 68.

An intermediate portion 15 of the li quid nozzle which is screw-threaded into .body 6| at the inner end of passage 63, has a passage 16 therethrough of smaller diameter than passage 83, and has at its rear end a tapered valve seat cooperating with the conical forward tip 11 on valve stem 18 to regulate the amount of liquid fed through passage 16. The passage 16 is diminished in bore at its inner end to form the liquid spray orifice l8. Held on to the inner end of the spray means body 6| by screw-threaded retaining ring is an air nozzle 8| which interfits with body 15 along contacting conical surfaces 19 and 82, on parts 15 and 8|, respectively. Air nozzle 8| has two sets of passages therein, a plurality of inner passages 83 equally spaced circumferentially and being located parallel to the passage 65, and two outer parallel passages 84, one at the top and the other at the bottom of the nozzle 8|. Passages 84 communicate with gas conducting passage 65 by means of the holes 85 through flange 86 and the passage around baffle 81; the inner passages 83 communicate with passage 65 through the space between flange 86 and body 75.

Outer passages 84 lead to outlet orifices located on the flared surface 89 of air nozzle 8|. Inner passages 83 lead to the approximately radially disposed passages 90 which lead the gaseous medium to an annular orifice 9| surrounding the central orifice I8.

Adhesive under pressure is fed through pipe 52, and during its passage it is heated to a freely mobile state by heating means such as steam in jacket 54. It then travels through passages 63, 16, and orifice 18, being limited in amount fed through the orifice by the position of needle valve H, which is adjusted by hand wheel 50.

A suitable gaseous medium is supplied under 7 pressure by pipe 41 in the amount determined by the setting of valve 41a to pipe 48 and thence to passages 65 83, 84 and orifices B8 and 9|. The liquid adhesive stream emerging from orifice 18 tends to expand gradually in diameter and the tubular gas sheath emerging from orifice 9| likewise expands in radial thickness both inwardly and outwardly. Consequently the gas sheath and the liquid stream impact against each other forwardly of the outlet of both, thereby atomizing the liquid into a forwardly diverging conical spray.

The gas emerging from the two orifices 88 impinges on this conical spray and produces a fiattened fan shaped spray lying in a plane through the axis of valve rod 18 and at right angles to the paper in Figure 7, the liquid in said spray I the air knife. This spray is met in the plenum chamber 30' of the air jet 30 bythe inrushing gaseous medium from pipe 34 through opening 34a, and because of the speed of the gas through opening 34a and thus the swirl and eddy which it creates within the said plenum chamber of the jet 30, the atomized liquid is thoroughly and uniformly mixed throughout the gas, so that a uniform mixture of gas and adhesive passes through throat 30" of the jet and issues from orifice 3| throughout the width thereof. The volume of gas entering through opening 34a is many times that entering through the spray devices. In some instances it may prove desirable, because of great width of the air jet 30, the character of the adhesive, etc., to supply the main body of gas to jet 30 from both ends thereof, in which case the feed line 34 shown at the right hand end of the jet in Figure 6 is duplicated to feed the gas to both the right and left hand ends of the jet.

It has been found that the character and composition of the main body of gas, entering the jet 30 through hose 34, and also that entering through pipe 41 by way of the spray devices is of particular importance in carrying out the described treatment of the sizing coat on an abrasive coated web. When the method diagrammatically illustrated by Figure 4 is carried out using as the sizing coat an adhesive that hardens by evaporation of a solvent, it is advisable to introduce a solvent of said adhesive into the gas entering through opening to prevent setting of the adhesive before it is cleared away from the tips of the granules or built up around the bases thereof. When using thermoplastic adhesives, the gas through opening 44 may be heated sufllciently to prevent premature chilling and hardening of the adhesive, and with certain adhesives,

there may be added both a solvent and heat to' the gas.

As an example, when hide glue is employed as the sizing coat on the abrasive coated web, the gas stream directed against the coated web may be humidified with water vapor, which is a solvent for the glue, and heated to a temperature of 150 F. or above. In actual practice it has been found convenient to use a mixture of compressed air and steam. The compressed air fed to hose 34 is heated to approximately 220 F. by means not shown, and suiiicient steam mixed therewith to saturate the air with water vapor. In certain instances dry steam may be used alone as the main supply of gaseous medium fed into the "air knife but for most purposes it is desirable to use a mixture of compressed air and steam. With certain adhesives, such as varnishes and synthetic resins of the alkyd, urea, and phenol formaldehyde types, which become softer and more liquid during the initial heating period, hot com pressed air is employed as the gaseous medium through hose 34, said air being heated to a temperature of 100 F. to 300 F., depending upon the particular solvent employed in the adhesive used.

The gaseous medium employed in the spray means may also diifer, depending on the character of the adhesive sprayed into the air knife" 30. If an animal or hide glue is employed, either steam or warm air which is saturated with moisa,s66,es6

ture may be employed as such gaseous medium. 7

When gum solutions or varnishes are used as such adhesive, steam or humidified air may not be required. In such cases a gaseous vehicle saturated with the solvent used for the adhesive may be employed.

The use of the "air knife" or gas jet with the incorporated spray means presents several advantages. The device is simple, easily controlled, and, by reason or its application of the additional adhesive at high velocity and in a finely divided state to the previously applied adhesive coating on the web, it produces a strong bond between the two. In the case in which the additional adhesive is waterproof, the high velocity application of it insures a complete sealing of the previously applied adhesive from the atmosphere.

Any variety of adhesive, such as glue, varnish, silicate, or synthetic resin, and any desired amount and viscosity of the adhesive may be used with the spray means incorporated in the "air knife;" and the amount and viscosity may be changed easily by altering the amount fed through the adjustable nozzle or opening into the air knife. Because of the high velocity-of gas entering and issuing from the air knife," no difficulty is experienced with building up a coating of adhesive on the inner-surfaces or orifice oi the "air knife," and thus the adjustment of the spray means the main gaseous medium supply, and the air knife orifice need not be disturbed after having once been set for a particular operation.

Although the spraying of an additional adhesive by the spray means associated with the air knife has been particularly described, other materials may obviously be sprayed into the plenum chamber of the air jet 30. Thus it may be desired to spray a tanning solution such as formaldehyde or potassium bichromate on to the sizing coat I, if such coat is an animal or hide glue, in order to render such sizing coat waterproof, simultaneously with the clearing of the abrasive granule tips by the air jet.

Having fully described the invention, I claim:

1. Apparatus for the manufacture of granular coated webs comprising means for moving and supporting a granular coated web, means to apply a layer .of adhesive to the granular coated side of the web, means to clear the still mobile adhesive from the tips of the abrasive granules and to apply a further layer of adhesive to the spaces between abrasive granules'consisting of a jet body comprising an elongated plenum chamber of relatively large cross sectional area, a throat chamber coextensive with the plenum chamber and formed by elongated lip portions converging from the plenum chamber to an elongated narrow discharge orifice, said throat chamber and said discharge orifice being of substantially the same length as the plenum chamber, said discharge orifice located substantially parallel to the length of the plenum chamber, transverse to the web, and near and directed toward the adhesive coated side of the web, means to supply a relatively large volume of a gaseous medium to the jet body cavity in a direction parallel to the length of the discharge orifice of the jet body, and means mounted on said jet body at a point remote from the elongated discharge ori- 'fice thereof to introduce into said gaseous memeans projecting the atomized adhesive in a di- I rection toward the discharge orifice of the jet body and substantially at right angles to the stream of the large volume of gaseous medium entering the jet body, whereby a thorough mixing of the gas and adhesive results and the adhesive content of the gas issuing from the elongated orifice is substantially uniform throughout the extent of the orifice.

2. Apparatus for the manufacture of granular coated webs comprising means for moving and supporting a granular coated web, means to apply a layer of liquid adhesive to the granular coated side of the web, means to clear the still mobile adhesive from the tips of the abrasive granules and to apply a further layer of adhesive to the spaces between the abrasive granules consisting of a jet body comprising an elongated plenum chamber of relatively large crosssectional area, a throat chamber coextensive with the plenum chamber, and formed by elongated lip portions converging from the plenum chamber to an elongated narrow discharge orifice, said throat chamber and said discharge orifice being of substantially the same length'as the plenum chamber, said discharge orifice lo-- cated substantially parallel to the length or the plenum chamber, transverse to the web, and near and directed toward the adhesive coated side of the web, means mounted on the jet body plenum chamber at a location remote from the discharge orifice and lying substantially in a plane which contains the discharge orifice and runs through the center of the plenum chamber for projecting atomized adhesive into the: plenum chamber in a direction toward said discharge orifice, said adhesive projecting means providing a substantially uniform adhesive spray in the rear of the plenum chamber and throughout the length thereof, and means for introducing a relatively large volume of a gaseous medium lengthwise of the plenum chamber in a direction substantially parallel to the lips of the discharge orifice and substantially at right angles to the direction in which the adhesive is projected by the adhesive projecting means, whereby the atomized adhesive 20 mixes thoroughly with the relatively large volume of gaseous medium and the gas discharged from the elongated orificecontains a substantially uniform amount of adhesive per unit volume at any point taken along the length of the orifice.

ROMIE L. MELTON. 

